When an oscillator being controlled is out of synchronization with its standard or reference oscillator, means must be provided for the output of the control circuit to capture the oscillator signal and to phase lock that signal to the reference oscillation. Numerous suggestions have been made in the past to increase the capture range of such control circuits. An example of this is described in German Pat. No. 1,140,969. In the case of initially switching on the circuit or of a failure of synchronization a control signal derived from the difference frequencies between the two oscillators occurs and a circuit is provided to produce a very low oscillation. If this oscillation is superimposed upon a subsequent adjusting voltage, the free-running oscillator can reach synchronization range. Since the alternating voltage corresponding to the difference frequency does not exist during synchronization, the criteria for the so-called "wobble" oscillator would also not exist during synchronization.